Like a lot of other Milsurp owners, I've spent time cleaning the Cosmoline (or whatever the foreign equivalent is called) out of Mausers, Mosin-Nagants, and Lee-Enfields. The consistency can range from a soft grease to that of road tar. I'm not an expert on preservation, but apparently decades of storage in grease doesn't harm or soften wood, or at least very little.

I know that the US has been using the barrier bag preservation method for a while, and it's certainly quicker and easier than grease.

Kind of made me wonder: Would long-term storage in Cosmoline/grease soften or otherwise deteriorate the plastics/polymers of modern firearms like the M4 carbine or Glock pistol?